An imprint method, which is one of microfabrication techniques, forms a desired pattern in a resin applied to a base plate by pressing a mold against the resin. After the pattern formed in the resin is coated with metal such as copper, the metal is flattened by grinding to form wiring on the base plate.
FIG. 13 depicts a process of forming wiring on the base plate. As depicted in FIG. 13A, a resin 52 is applied to a base plate 51. Next, as depicted in FIG. 13B, a mold 53 is pressed against the resin 52 to form a pattern in the resin 52. Next, as depicted in FIG. 13C, the remaining film of the resin 52 is removed by anisotropic etching. Next, as depicted in FIG. 13D, the pattern formed in the resin 52 is coated with copper 54. Next, as depicted in FIG. 13E, the copper 54 is flattened by grinding to form wiring 55 on the base plate 51. In addition, a plurality of layers of wiring 55 are formed on the base plate 51 by repeating the process depicted in FIGS. 13A to 13E.
Japanese Laid-open Patent Publication No. 08-245225 and Japanese National Publication of International Patent Application No. 2004-504718 are examples of related art.
When the mold 53 makes contact with the resin 52 in a process of forming a pattern in the resin 52, the resin 52 climbs the wall of the mold 53 due to capillary phenomenon. When the mold 53 is pressed against the resin 52, the resin 52 is extruded by the mold 53 and a protrusion of the resin 52 is formed around the mold 53, as depicted in FIG. 14. If there is a climbing section of the resin 52 on the wall of the mold 53, the climbing section of the resin 52 is stripped in a process of flattening metal and the pattern surface of the resin 52 is damaged by the stripped resin 52.
There are methods of removing the protrusion of the resin 52: a method of scraping the resin 52 with a squeegee, a method of decomposing the resin 52 with plasma, and a method of dissolving the resin 52 with a solvent. When the protrusion of the resin 52 is removed by scraping the protrusion with a squeegee 56, a resin layer 57, formed on the wall of the mold 53, is not removed and left as a sharp protrusion, as depicted in FIG. 15. In this case, the resin layer 57 is stripped in a process of flattening metal and the stripped resin layer 57 damages the pattern surface of the resin 52, thereby degrading the product quality. An additional process of removing the stripped resin layer 57 that avoids the pattern surface of the resin 52 from being damaged by the stripped resin layer 57 increases cost.
When the protrusion of the resin 52 is removed by decomposing the resin 52 with plasma, high energy of plasma damages the base board 51 and the mold 53, thereby degrading the product quality. When the protrusion of the resin 52 is removed by dissolving the resin 52 with a solvent 58, the solvent 58 penetrates the resin 52 in which a pattern has been formed as depicted in FIG. 16, thereby degrading the product quality. In addition, an additional rinse process of removing the solvent 58 increases cost.
There is a method of suppressing the generation of a protrusion of the resin 52. In this method, the mold 53 larger than the base plate 51 is pressed against the resin 52 as depicted in FIG. 17A. As depicted in FIG. 17B, bubbles 59 are caught in a concavo-convex pattern of the mold 53 when the mold 53 is pressed against the resin 52. As depicted in FIG. 17C, when the mold 53 is further pressed against the resin 52, the bubbles 59 move toward the outside of the mold 53. As depicted in FIG. 17D, as the gap between the mold 53 and the base plate 51 becomes smaller, the flow resistance of the resin 52 increases and the bubbles 59 between the concavo-convex pattern of the mold 53 and the resin 52 are hard to release, thereby degrading the quality of the pattern formed in the resin 52.
The purpose of this disclosure is to provide a technology for avoiding a resin from climbing the wall of a mold and removing the protrusion of the resin.